High-resolution simulation of film cooling with blowing ratio and inclination angle effects based on hybrid thermal lattice Boltzmann method

A series of high-resolution simulations on film cooling with varying blowing ratios and inclination angles are carried out by using in-house code based on hybrid thermal lattice Boltzmann method. Three blowing ratios ranging from 0.2 to 0.8 and four inclination angles from 15? to 60? are chosen for the simulations. The evolutionary mechanism of coherent structure in three domains of film-covering region is studied from the view of space and time. Besides, the influencing mechanism of blowing ratio and inclination angle on flow and heat-transfer features of film cooling is uncovered. Results show that hairpin vortex, hairpin packet and quasi-stream-wise vortex appearing in rotating domain play a key role in heat-transfer process of film cooling. The strong ejection, sweep and vortex rotation resulted from these vortices enhance the convective heat transfer. It is also found that the size of coherent structure varies significantly with blowing ratio and its integral form shows a strong dependence on inclination angle. Moreover, inclination angle of coolant jet has a significant impact on turbulence fluctuation intensity. The influence of blowing ratio on the attachment of coolant film and film-cooling performance is more obvious than that of inclination angle. It is believed that all of these are related closely to the variation of stream-wise and wall-normal jet velocity in the case of various blowing ratios and inclination angles.

Upper Openings Ventilation System Study of the Building by the Lattice Boltzmann Model

We present in this work a numerical study of a ventilation system in a room with two openings in the ceiling and a floor heating indicated by constant heat temperature. The double population thermal lattice Boltzmann method is used, with nine velocities model D2Q9 for the dynamic field and a five velocities model D2Q5 for the temperature field. The results are presented in the form of streamlines, temperature contour and velocity profile, and analysed as a function of the Richardson number.

Advanced thermal lattice Boltzmann method for the simulation of latent heat thermal energy in a porous storage unit

The current research expounds numerical investigation of key parameters effects, namely porosity ( ε= 0.4, 0.6, 0.7 and 0.8), Reynolds number (Re = 100, 200, 400 and 600) and Eckert number (Ec= 0, 1, 5 and 10) on the forced convective laminar flow and heat transfer through a horizontal porous channel filled with a metal foam structure impregnated with paraffin as a phase change material (PCM). The Darcy-Brinkman-Forchheimer model under the local thermal non-equilibrium (LTNE) condition is deemed at the representative elementary volume (REV) scale. The fully coupled equations of Navier-Stokes, Poisson’s equation, energy equations, and continuity equation were handled numerically via a thermal single relaxation time lattice Boltzmann method (TSRT-LBM). To facilitate implementation, all LB equations are based on the same speed discretization scheme (D2Q9). Three-population distribution functions were applied to simulate the fluid flow, and temperatures of the fluid and solid phases. Previously, the numerical model was validated by available cases. Then, a comprehensive investigation has been performed to investigate the influence of the aforementioned dimensionless numbers. All LBM results are found to be highly consistent with other numerical works. The outcomes reported that at lower porosities, the energy and exergy efficiencies increased with increasing Re and Ec. However, for large porosity values, the efficiencies were optimum for a critical Re ~ 400. To sum up, it can be stated that the implemented thermal lattice Boltzmann method has been demonstrated as a suitable approach study the thermal sensible energy storage.